The present disclosure relates generally to remote controlled locomotives and, more particularly, to a method and system for coordinated transfer of control of a remote controlled locomotive.
The remote control operation of a locomotive is useful for allowing a ground-based operator to control the locomotive from trackside in a switching yard. A remote control unit typically includes one or more hand held transmitting units for communicating with a controller on the locomotive. This type of system permits an operator to perform such operations as coupling and uncoupling cars while retaining control over the speed of the locomotive by manually regulating the throttle and brake systems.
Since a remote control system can be used in conjunction with a train having multiple cars, it may be the case that an individual system operator cannot adequately view all of the cars at once. Accordingly, there are systems in existence that allow two or more operators to monitor different sections of the train. For example, in a two-operator system, each operator has a hand held transmitting unit, each of which has the capability of transmitting the full set of remote control commands to the locomotive. For obvious reasons, the system is designed such that (with the exception of certain commands) the controller on the locomotive will only accept commands from one of the transmitters at any given point in time. However, because it is desirable to be able to selectively designate which of the hand held controllers will have “command authority”, there is a need to coordinate and control such a transfer of command authority in an appropriate and effective manner.
U.S. Pat. No. 5,685,507 issued to Horst, et al. discloses a remote locomotive control system in which the transfer of command authority from one transmitter to another is processed and executed by a slave controller mounted on board the locomotive. The slave controller initially assigns a “command authority holder status” to one of the transmitters and a “command authority non-holder status” to another of the transmitters. The slave controller keeps track of the current command authority holding transmitter by including a memory portion that associates a specific transmitter identifier with the command authority holder. When it is desired to change the command authority from the current command authority holder to a current command authority non-holder, the slave controller receives a transfer command signal from the transmitter having the command authority. Assuming certain safety checks are first met, if a command authority non-holder transmitter acknowledges (within 10 seconds) the transfer request by an appropriate signal (in this case, by transmitting a “reset” bit set at high), then the CPU within the slave controller shifts in memory the identifier associated with the reset bit at high to the position of the current command holder.
Essentially, the slave controller is the entity that determines which transmitter has the control authority. Each command signal sent by a given transmitter includes an identifier therewith, which identifies the specific transmitter sending the command signal. Depending upon the command sent, the slave controller then examines the identifier to see whether the command comes from the command authority holder.
A drawback, however, of the system in '507 patent stems from the fact that it is the slave controller (remotely located on board an unmanned locomotive) that ultimately has the responsibility of assigning and determining which transmitter has the command authority, as well as implementing a change in the command authority. If there is any problem with system hardware, software, or even with external operator-to-operator coordination, then there is no person “in the loop” to manage an unexpected or erroneous transfer of authority.